A filament eruption spanning approximately 25° occurred in Active Region 4403 at 23:28 UTC on April 1, in association with a C6.1 solar flare. The bulk of the ejecta propagated toward the north-northwest, largely offset from the Sun–Earth line.
An associated coronal mass ejection (CME) was detected at 23:45 UTC in GOES CCOR-1 coronagraph imagery. The CME exhibited an asymmetric halo structure, indicating that part of the expanding plasma cloud intersects the observational plane surrounding Earth, while the main ejecta remains directed away from the planet.
Initial model estimates suggest that the CME is likely to pass predominantly north of Earth’s orbital path, with only a peripheral interaction possible. This geometry supports a glancing blow scenario, where Earth encounters the flank of the CME rather than its central region.
Glancing interactions usually result in reduced energy transfer into the magnetosphere compared to direct impacts.
Forecast confidence in the exact arrival time remains limited due to gaps in coronagraph imagery, which constrain model initialization and propagation accuracy. Current estimates place the potential interaction window in the early UTC hours of April 4.
If the CME’s magnetic field contains sustained southward components upon arrival, minor geomagnetic storm conditions at G1 – Minor level are possible, with a chance of reaching G2 – Moderate levels under more efficient solar wind-magnetosphere coupling. The magnitude of the response will depend primarily on the orientation and persistence of the interplanetary magnetic field.
Geomagnetic conditions on April 2 remain elevated under the combined influence of a coronal mass ejection that impacted Earth on March 30 and the ongoing onset of a coronal hole high-speed stream (CH HSS).
This pre-conditioned solar wind environment may enhance the magnetospheric response to even a glancing CME interaction, increasing variability in geomagnetic activity through April 4.
High-speed stream conditions are expected to persist through April 3, maintaining unsettled to active geomagnetic levels before the potential arrival of the April 1 CME. Intermittent enhancements in geomagnetic activity are expected, up to G2 – Moderate levels, though no severe storm conditions are currently supported by available data.
Auroral activity may expand to lower latitudes during periods of peak geomagnetic disturbance, while minor impacts to high-frequency radio communication and satellite-based navigation systems remain possible.
No significant radiation storm conditions are expected from this event.
References:
1 Forecast Discussion – NOAA/SWPC – Issued at 12:30 UTC on April 2, 2026